London, Nov 17 (IANS): Serbia's Novak Djokovic defeated Marin Cilic 7-6 (9-7), 6-2 in his final group stage match at the Association of Tennis Professionals (ATP) Finals and heads into the weekend as the clear favourite to win a record-tying sixth title.

The world No. 1 had already booked a spot in the semi-finals of tennis' elite season-ending event by winning his first two matches in the group stage against American John Isner and Germany's Alexander Zverev, reports Efe news.

Both of those previous wins were also in straight sets.

Although he nearly dropped his first set of the tournament against the Croatian, the Serbian's rock-solid baseline play, phenomenal defence and outstanding serve eventually gave him the clear edge over his big-hitting opponent on Friday night.

The first set at London's O2 Arena came down to a tie-breaker after both players did an excellent job of controlling their service games.

That trend continued in the tie-break, as the servers won the first 14 points before Djokovic finally got a key mini-break to go ahead 8-7 and then finished off the set a point later.

The Serbian had to save a set point in the tie-break when serving at 5-6.

Cilic fended off the one break point he faced in the opener and won 86 percent of his first-serve points, while Djokovic lost just two of his 34 service points.

The Croatian, however, was unable to maintain his level in the second set, dropping serve twice as Djokovic pulled away to win the last four games of the match.

Djokovic finished the contest with a 90 percent winning percentage on first-serve points and a phenomenal 91 percent winning percentage on second-serve points.

The 14-time Grand Slam champion will next take on South African world No. 6 Kevin Anderson, runner-up in the semi-finals. That Saturday night contest will be a rematch of this year's Wimbledon final, which Djokovic won in straight sets.

Saturday's first semi-final will pit 37-year-old Swiss world No. 3 Roger Federer, winner of a record six ATP Finals titles, against 21-year-old German world No. 5 Alexander Zverev.